Analog computing circuits for absolute values



Feb. 4, 1969 v I KATSUMI TAKEMURA ,4

ANALOG COMPUTING CIRCUITS FOR ABSOLUTE VALUES Filed June 5, 1964 van/roekn Tamra Tnam M we ATTORNEY United States Patent 3s/30,ss4 U.S. Cl.235-197 Int. Cl. G06g 7/26, 7/28,- G06f 15/34 4 Claims ABSTRACT OF THEDISCLOSURE An analog computing circuit formed by a magnetic operationalamplifier having two control windings operated in accordance with theampere-turns given by two control windings, each being independentlycontrollable. The polarity of the output signal obtained from thecircuit is determined by the direction of the ampere-turns of thecontrol windings which is unchanged regardless of the polarity of theinput signals. This property is utilized to obtain an operationalcircuit for calculating absolute values. The input signal is supplied toeach control winding through a diode in a manner to cause the controlwindings to generate a unidirectional ampere-turn regardless of thepolarity of the input signals.

This invention relates to analog computing circuits for obtaining outputsignals of definite polarity proportional to the magnitudes of inputsignals but independent of polarities of input signals, the outputsignals thus representing the absolute values.

The primary object of the present invention is to provide an operationalcircuit of the kind specified which is simple and compact inconstruction and reliable in operation.

There are other objects and particularities of the present invention,which will be made obvious in the following detailed descriptions withreference to the accompanying drawings, in which;

FIG. 1 is a diagram of conventional operational circuit;

FIG. 2 is a diagram showing an operational amplifier utilized in thepresent invention;

FIG. 3 diagrammatically shows an embodiment of the present invention;and

FIG. 4 shows an input-output characteristic of the present invention.

Referring to FIG. 1, a conventional operational circuit for obtainingabsolute values of signals is usually formed by two computingelements,'that is, a function generator 1 having -2-times gain forpositive input signals, for example, while zero-gain for negative inputsignals, and a summing amplifier 2 for providing the sums of inputsignals themselves and outputs of function generator 1.

With such a construction,

where V is the output voltage, and V is the input voltage. However, theneed of two computing elements makes the operational circuit complex inconstruction, and large in size.

The present invention provides an operational circuit for obtainingabsolute values of signals, simple and compact in construction by properutilization of magnetic amplifier.

Referring now to FIG. 2, the magnetic operational amplifier 3 formingthe main part of the present invention is a push-pull amplifier ofself-feedback type, which includes an internal first feedback pathcomprised by an impedance 13 for positive voltage feedback from theoutput side to have substantially infinite gain over the whole range ofoutput. In addition, the internal first feedback path provides positivefeedback of output current to compensate for load-voltage variation dueto load current. The amplifier 3 has control windings 4 and 5, which maybe used independently of each other or may be used in series with eachother.

In order to employ this operational amplifier as an analog computingelement, the input signal is applied to the control winding 4 through aninput impedance R and the output signal is fed back through a secondfeedback path comprised by a feedback impedance Rf, as is wellknown. Theamplifier operates so that the ampere-turn due to current flowingthrough the control winding is substantially zero, and then the relationbetween input signal V and output signal V is o i Thus, any desirableanalog computing element may be obtained.

As can be seen from the name, the above-described magnetic operationalamplifier operates in accordance with ampere-turns given by two controlwindings which may be controlled independently of each other. Thepresent invention utilizes such an amplifier in a proper and uniquemanner.

Referring to FIG. 3, the embodiment shown comprises the magneticoperational amplifier 3, with control windings 4 and 5 connected inseries. The outer ends of seriesconnected windings 4 and 5 are connectedto an input terminal 7, through a diode D and input impedance R inseries, and a diode D and input impedance R in series, respectively.Diodes D and D are disposed in opposite-conduction sense to each other.The output is fed back to the outer end of winding 4 through a feedbackimpedance Rf. Input signal V is applied between input terminal 7 and theground, while output signal V appears between output terminal 6 and theground.

When V is positive, diode D is conductive to supply ampere-turns toamplifier 3, for providing output V which is opposite in polarity to theinput V, and is of magnitude determined by R /R When V is negative,diode D conducts to supply ampere-turns to amplifier 3. The direction ofampere-turns thus supplied is same as when V is positive. Thus, theoutput voltage V is same in polarity with the input, and of a magnitudedetermined by R /R FIG. 4 shows such an input-output characteristic.

What is claimed is:

1. Analog computing circuit for absolute value comprising a magneticamplifier which is provided with a first feedback path for positivefeedback of output voltage to assure substantially infinite gain overthe whole range of the output and positive feedback of output current tocompensate for variations in the load voltage due to load current, twocontrol windings independent of each other for controlling theamplifier, an input terminal, two sets each having a series-connecteddiode and input impedance, each set being connected between said inputterminal and one terminal of each of said control windings in suchmanner that the polarity of said diodes are mutually opposite and thatthe sense of the magnetic field produced by said control windings are inthe same direction, and second feedback path means for negativelyfeeding back the output of said amplifier to said terminal of one ofsaid control windings.

2. An analog computing circuit according to claim 1 wherein the secondnegative feedback path means has an impedance value R the inputimpedance of that set connected to said one of said control windingshaving the output of the amplifier fed back thereto has an impedancevalue R and the output signal V is related to the input signal V; by therelationship V /V =R /R 3. An analog computing circuit according toclaim 1 wherein an input signal is applied to the circuit between theinput terminal and ground, an output signal is obtained from the circuitbetween an output terminal thereof and ground, and the remainingterminals of the two serially connected control windings are connectedto ground.

4. An analog computing circuit according to claim 3 wherein the secondnegative feedback path means has an impedance value Rf, the inputimpedance of that set connected to said one of said control windingshaving the output of the amplifier fed back thereto has an impedancevalue R and the output signal V is related to the input signal V by therelationship V /V =R;/R

References Cited UNITED STATES PATENTS 0 MALCOLM A. MORRISON, PrimaryExaminer.

ROBERT W. WEIG, Assistant Examiner.

US. Cl. X.R.

